A Study of Glass Transition of Polymeric Materials by Specific Heat Spectroscopy

1.使用了自行研制的交流量热实验系统。用FFT分析器代替锁相放大器，缩短了测量时间.传统的交流量热系统使用带孔的旋转板作为光调制器，用于周期性地加热样品。本课题采用两块偏振片作为光调制器，其中一块偏振片旋转，另一块偏振片固定，得到正弦光强。采用步进电机使加热频率更加精确.对微机控制整个实验系统的程序进行了修改，使之适合FFT分析仪和步进式砂浆控制器。利用新的程序可以连续改变加热频率进行测量.对聚苯乙烯（MW=2000）进行初步测量。测量时间小于使用锁定放大器的常规方法的测量时间的十分之一。该项目的主要目标是缩短测量时间。这一新的实验系统将推动对高分子材料性能有重要影响的热历史研究.目前，加热频率限制在0.5Hz至30Hz范围内。扩展频率范围是未来的问题。

1. An experimental system of AC calorimetry constructed in our laboratory was used. The lock-in amplifier used in the system was replaced with FFT analizer to make measuring time shorter.2. Conventional AC calorimetry system uses a rotating plate with holes as the light modulator for periodic heating of the sample. In this project two polarizing plates, one of which is rotated and the other is fixed, were employed as the light modulator to obtain sinusoidal light intensity. The heating frequency became much more accurate by using a stepping motor.3. The program of the personal computer to control the whole experimental system was changed to fit the FFT analyzer and the stepping mortar controller. Using the new program we can make measurement changing the heating frequency successively.4. Preliminary measurement was made for Polystylen (MW=2000). The measuring time was less than one tenth of the measuring time of the conventional method using a lock-in amplifier. The main object of this project to make the measuring time shorter was carried out. Study of the thermal history which is important for the properties of polymeric materials will be progressed by this new experimental system.5. The heating frequency is limited in the range of 0.5Hz to 30Hz at present. To expand the frequency range is left as a future problem.